Machine for grinding large-area workpieces



1970 K. HEESEMANN 3,53 MACHINE FOR GRINDING LARGE-AREA WORKIl EGlf-SFiled Nov. 13, 1967 4 Sheets-Sheet 1 Fig] Inventor ATTY Z Dec. 1, 1970 4K. HEESEMANN 3,543,443

MACHINE FOR GRINDING LARGE-AREA WORKPIECES Filed Nov. 13, 1967 4Sheets-Sheet 2 Fig.3

lnvenlor: KARL HEEJEMANA/ Dec. 1, 1970 K. HEESEMANN 3,543,443

MACHINE FOR GRINDING LARGE-AREA WORKPIECES Filed Nov. 13, 1967 4Sheets-Sheet 5 Inventor.- KARL H5555 MAN/V ATTYS.

Dec. 1, 1970 K. HEESEMANN 3,543,443

- MAQHINE FOR GRINDING LARGE-AREA WORKPIECES Filed Nov. V13, 1967 4Sheets-Sheet 4:

Fig.5

Fig.6 6?

Inventor:

K ARL HEA'SEMANN United States Patent 3,543,443 MACHINE FOR GRINDINGLARGE-AREA WORKPIECES Karl Heesemann, 54 Friedenstrasse, BadOeynhausen-Rehme, Germany Filed Nov. 13, 1967, Ser. No. 682,270 Claimspriority, application Austria, Nov. 11, 1966, A 10,443/ 66 Int. Cl. B24b7/00, 9/00, 21/00 US. Cl. 51-3 24 Claims ABSTRACT OF THE DISCLOSUREBACKGROUND OF THE INVENTION This invention relates to a method of and amachine for automatically fine and subsequently very fine grinding oflarge-area workpieces.

The fine and very fine grinding of veneered, lacquered or otherwiselaminated and also of solid workpieces having large surface areas isexecuted at present in a known and advantageous manner by cross grindingon two separate automatic belt-grinding machines.

In regard to surface make up, grinding out of the surface and depth ofgrind, cross grinding yields the best grinding quality. Here thepre-grinding is carried out as a transverse grinding, i.e. across thegrain, and the finishgrinding as a longitudinal grinding, i.e. parallelto the grain.

Since in conventional machines the workpieces must be fed longitudinallyfor the transverse grinding and crosswise for the longitudinal grinding,it is necessary to change the direction of travel of the workpieces by90 between the longitudinal and the transverse grinding. Thus, for thetransverse and the longitudinal grinding separate machines must be usedwhich are to be connected with each other by a so-called angle deliveryapparatus so that the direction of travel of the workpieces undergoesthe necessary change between the first and the second machines. Suchinstallations call for high investments and require a large area forchanging the direction of the workpieces passing through the machines.Moreover, due to the inertia of the workpieces, the speed of passage ofthe workpieces is limited during the direction change.

So far as the known wide belt grinding machines have been used as thesecond machine it has shown that these machines are not able to producea very fine grinding of adequate quality since the feed direction of theworkpieces and the running direction of the grinding belt extendparallel to each other. Since thus the grinding is not crosswise andtherefore the grinding defects and traces add to each other instead ofcompensating for one another, the ground surfaces remain rough.

Furthermore, the grinding belt is always only worn out in the area whichcorresponds to the workpieces being ground. The hard glue joints, forexample, which normally reoccur on the same lines on the workpiecesalways wear the grinding belt along the same longitudinal strips. Thegrinding belt subsequently clogs on these longitudinal 3,543,443Patented Dec. 1, 1970 SUMMARY OF THE INVENTION It is the object of thepresent invention to avoid the disadvantages mentioned above and toprovide an eflicient method of cross grinding large-area workpieces, anda machine for carrying out that method; which method comprises the stepsof first grinding the workpieces transverse to their direction of feed,and subsequently grinding the workpieces substantially parallel to saiddirection of feed.

An important feature of the invention consists in that transversegrinding motions may be carried out when grinding the workpecessubstantially parallel to their direction of feed.

The machine for carrying out the method comprises two supports, railsconnecting said supports, a drive roller and an idler roller supportedby said supports, a conveyor belt led around said rollers for feedingworkpieces to be ground and moving preferably in one and the samedirection, at least one transverse grinding mechanism mounted on one ofsaid rails, a longitudinal grinding mechanism arranged downstream of thetransverse grinding mechanism, and means for moving said longitudinalgrinding mechanism to and fro relative to the workpieces passingthrough.

In an advantageous form of construction more than one transversegrinding mechanisms are arranged one behind the other and are eachprovided with a resilient pressure beam and an endless laminatedpressure belt inserted between the grinding belt of the transversegrinding mechanism and said pressure beam.

The longitudinal grinding mechanism is preferably pro vided with ato-and-fro movable, advantageously endless grinding belt pressed againstthe workpieces to be ground by a pressure beam pressing against itsinner side, while the grinding belt is equipped with a device to adjustit to run in the center of its drive and guide roller.

In a particularly advantageous embodiment of the longitudinal grindingmechanism the grinding belt drive and the guiding members as well as, ifnecessary, the pressure beam with its holding mechanism are mounted on aguide member movable transverse to the direction of travel of theworkpieces. For this purpose a device such as a spindle may be provided.

It is further proposed by the invention constantly to change theeffective pressing area of the grinding belt corresponding to the widthof the workpieces in order to avoid cutting through the edges of theworkpieces.

Another embodiment of the invention is possible wherein not the wholelongitudinal grinding belt mechanism, but only its grinding belt ismoved to and fro transverse to the direction of travel of the workpiecesby a special controlling means.

The machine proposed by the invention excels in that the traces of thegrinding are in an advantageous manner compensated while the workpieceruns through the machine in one and the same direction.

BRIEF DESCRIPTION OF THE DRAWINGS One embodiment of the invention willnow be described by way of example and with reference to theaccompanying drawings, in which:

FIG. 1 is a schematic side view of a cross grinding machine according tothe invention;

FIG. 2 is a cross section on the line 11-11 of FIG. 1;

FIG. 3 is a cross section through the guide member of the machine withan enclosing traverse and the grinding belt;

FIG. 4 is a front view, partly in cross section, of the pressure beam ofthe cross grinding machine;

FIG. is a cross section on the line VV of FIG. 4

and FIG. 6 is a cross section on the line VIVI of FIG. 4.

DESCRIPTION OF THE PREFERRED EMBODIMENT FIGS.1 and 2 show a cross beltgrinding machine 10 mounted on two supports 11 and 12 connected by twolower connecting rails 13 and 14. An endless conveyor belt 15 forfeeding workpieces 52a is led around a drive roller 15b and an idlerroller 15a. A motor (not shown) drives the drive roller 15b and thus theconveyor belt 15 through an infinitely variable gear unit in preferablyone and the same direction.

As shown in FIG. 1, two transverse grinding mechanisms 7 and 18 arefixed at a distance from one another on an upper connecting rail 16extending between the supports 11 and 12 and are provided with twovertically adjustable pressure beams. It is self-evident that instead oftwo, also one or more than two tranverse grinding mechanisms may beprovided which in the latter case are arranged one behind the other.Pressure rollers 19, and 21, 22 which may each be composed of many smallrollers are arranged on each side of the two pressure beams of the twotransverse grinding mechanisms 17 and 18 respectively. A contact rolleris arranged in the same plane as the pressure rollers 19 and 21 and isactuated by the passing workpiece 52a to control the vertical movementsof the pressure beams. The pressure beams are provided with mechanisms(not shown) with which the working width can be adjusted according tothe width of the workpieces 52a passing through the machine. When deemednecessary an endless laminated pressure belt (not shown) may be insertedbetween the grinding belt and the pressure beam of the transversegrinding mechanisms 17 and 18. A longitudinal grinding mechanism 23 witha pressure beam 23a is arranged downstream of the two transversegrinding mechanisms 17 and 18. This longitudinal grinding mechanism 23is designed as a wide belt grinding machine and comprises a fixedbox-shaped guide member 24 which is mounted at one of its ends throughthe intermediary of a carrier arm 25 on the support 11 and is braced atits other end against the support 12 by a pivotable support 26. Theconnection between the pivotable support 26 and the support 12 can bedisengaged, for example, when the grinding belt must be replaced, bymeans of a locking device like a locking lever 26a.

Two end plates 28 and 29, between which a traverse 30 which partlysurrounds the guide member 24 is fixed,

are guided by means of guide rollers 31 on the box-shaped I guide member24 which for example is provided with four guideways 27 bevelled on theedges of its length, so as to be rollable in a direction transverse tothat of the workpieces 52a. Lateral sleeves 30a surround the parts ofthe guide member 24 which are not surrounded by the traverse 30. A driveroller 32 for a wide endless grinding belt 34 is driven by a motor 32aand rotatably mounted on an arbor 37 extending between the upper ends ofthe end plates 28 and 29. This wide endless grinding belt 34 is ledaround this drive roller 32 and lower guide rollers 35 and 36 locateddownstream and upstream of the pressure beam 23a. The grinding belt 34is tensioned by means of a compressed air cylinder 38 with a piston rod38a through parallel rods 39. This air cylinder 38 is mounted on thetraverse 30. In order to maintain the grinding belt 34 in the middleportion of the drive roller 32, an electropneumatic control device whichcomprises for example a compressed air cylinder 40 is provided, throughthe intermediary of which the arbor 37 of the drive roller 32 is movedabout a universal joint 41 or the like when one of the edges of grindingbelt 34 touches one of lateral limit switches (not shown) located in theimmediate vicinity of the edges of the grinding belt 34.

The traverse 30 with the end plates 28 and 29 and the further parts ofthe longitudinal grinding machine 23 connected thereto are movable onthe guide member 24 by a reversible motor 42 connected to a spindle 43passing through a spindle nut 44 built into the end plate 29. Theto-and-fro motions produced by the reversible motor 42 of theabove-mentioned parts of the longitudinal grinding mechanism 23 arelimited by limit switches 45 and 46 which effect the reversal of themotor 42 whenever these moving parts reach an end position. The extentof the to-and-fro motions is adjustable by displacing the limit switch45 on a rail 47.

The pressure beam 23a is vertically adjustable in the end plates 28 and29 by means of a parallel linkage system 48. Pressure rollers 49 and 50,which may consist of a plurality of small rollers, are provideddownstream and upstream of the guide rollers 35 and 36 for the grindingbelt 34 to guide the workpieces 52a on the conveyor belt 15. A contactroller (not shown) is arranged in the same plane as the pressure rolleror rollers 50 and is activated by the passing workpieces 52aautomatically to control the upwards and downwards motions of thepressure beam 23a acted upon by a compressed air cylinder 51, its pistonrod 51a and a shaft 5111 (FIG. 5). To achieve this end, clamping collars51g are fixed on the shaft 51b mounted in mountings 510 which collars51g carry the pressure beam 23a at its ends through the intermediary oflevers 51d and 51e with a carrier foot 51 As the shaft 51b turns, thepressure beam 23a lowers or raises.

In order completely to grind the surfaces of the Workpieces 52a runningstraight through the machine while not cutting through its edges, thepressure surface of the pressure beam 23a moving to and fro with themovable parts of the longitudinal grinding mechanism 23 is controlled byan adjustment mechanism. This adjustment mechanism comprises a devicefor pre-adjustment according to the width of the passing-throughworkpieces 52a as well as an automatically working mechanism which areboth dependent on contact roller control and reverse motions foradapting the pressure surface of the pressure beam 23a to the workpieces52a guided by a guide bar 52.

The guide member 24 is closed at its free end by an end plate 53 (FIG.2) on the upper end of WhlCh the reversible motor 42 and the spindle 43are located. The lower end of this end plate 53 is provided with avertical guiding device 54 (FIG. 4) in which one end of a guide rail 55is guided so as to be unshiftable in its axial direction, whereas itsother end rests in another vertical guiding device 56 arranged on thecarrier arm 25. The vertical guiding devices 54 and 56 permit the guiderail 55 extending through the pressure beam 23a to move up and down withthe same.

Because of its indirect connection with the end plates 28 and 29, thepressure beam 23a can move to-and-fro transverse to the direction theworkpieces 52a are fed through the machine. The guide rail 55 in thepressure beam 23a is guided in a suitable way, for example by ballbearings and rollers 55a (FIG. 5 which are adapted to the particularprofiling of the guide rail 55. As shown in FIG. 4, sliding rails 57 and58 are guided to be movable and lockable in the guide rail 55, whichsliding rails 57 and 58 are provided with oblique surfaces 57a and 5812at the ends pointing towards one another. These oblique surfaces 57a and58a extend adjacent both longitudinal edges of the workpieces 52apassing through the machine and their slope corresponds to the necessaryslight slope of the lower pressure surface of the pressure beam 23aconstructed as a steel plate 65. For pre-adjustment and locking, thesliding rail 58 is provided with holes 59 in which a lock pin 60 engagesaccording to the width of the workpieces 52a passing through themachine, which lock pin 60 is passed on boht sides of the sliding rail58 through a fork-shaped member 61 on the guide rail 55.

As shown in FIG. 6, the steel plate 65 is carried by the lower ends oflifting rods 66 and 67 fixed intermediate the two longitudinal edges ofthe steel plate 65. The upper ends of the lifting rods 66 and 67 arescrewed into pivoting levers 68 and 69 fixed as well as a pivoting lever70 on a common shaft 73 rotatably mounted in bearing blocks 71 and 72.On its free end the pivoting lever 70 carries a roller 74 which rolls onthe sliding rails 57 and 58, respectively, during the to-and-fro motionsof the pressure beam 23a.

The sliding rail 58 can be so adjusted that the gap between the freeends of the sliding rails 57 and 58 corresponds to the width of theworkpieces 52a. Thereby the pressure surface of the pressure beam 23a,1.65. the steel plate 65, presses always only there on the gl'lIldll'lgbelt 34 where a workpiece 52a under the pressure beam 23a 1s located,regardless of the to-and-fro motions of the pressure beam 23a.

The cross belt grinding machine operates as follows:

For grinding uniform workpieces 52a of a given width, the correspondingworking width on the two pressure beams of the transverse grindingmechanisms 17 and 18 and on the sliding rail 58 of the pressure beam 23aas well as the extent of to-and-fro motions controlled by the limitswitches 45 and 46 are adjusted. When the width of the workpieces 52a isnot larger than the difference between the maximum width of the grindingbelt 34 and the maximum to-and-fro motion limit, the full effectiveto-andfro motion limit will be effective in the described embodiment ofthe invention.

The workpieces 52a on the conveyor belt pass through underneath thepressure beams of the transverse grinding mechanisms 17 and 18 and thepressure beam 23a, which beams thereby are brought into and out ofengagement with the workpieces 52a by the contact rollers arranged ontheir impact sides in a known manner.

In order to attain the best possible quality of grinding by crossgrinding the traces of grinding, the pressure beam 23a and theretoconnected parts of the longitudinal grinding mechanism 23 are movedwithin the set limits continually to and fro crosswise to the directionof feed of the workpieces 52a. The to-and-fro motions are transmittedfrom the reversible motor 42 through the spindle 43 to the reciprocatingparts of the longitudinal grinding mechanism 23. At the end of eachmotion the limit switch 45 or the limit switch 46 is actuated by itscooperating end plate 28 or 29 whereby the reversible motor 42 and theirdirection of rotation of the spindle 43 are reversed. The wide grindingbelt 34 participates in these to-and-fro motions. The lateral thrustsresulting during the grinding operation lessen lateral disorientation ofthe grinding belt 34 which entails that the described mechanisms forcentering the grinding belt 34 need be less effective while effecting abetter grinding.

The pressure beam 23a also participates in these toand-fro motions.Since on the one hand the workpiece 52a passes through the machine in astraight line and does not participate in the to-and-fro motionstransverse to the feed direction, and on the other hand it must becontacted continuously as it passes through underneath the pressure beam23a on its whole width by the grinding belt 34 pressed on by thepressure beam 23a, it is preferable that the actually effective pressingsurface of the steel plate 65 displaces constantly on the same. To thisend, the rollers 74 roll alternately on the locked sliding rails 57 and58 in dependence on the adjustments for the to-and-fro movement and thewidth of the workpiece 52a or they are in the space between the two freeends of the sliding rails 57 and 58 above the workpiece 52a where theyexecute no function. Then, just at the certain moment of the to-andfromotions when the rollers 74 do not roll on the sliding rail 57 or 58,the lifting rods 66 and 67 are in their lowest positions and thecorresponding region of the pressing surface of the pressure beam 23apresses the grinding belt 34 during the grinding operation against thepassing through workpiece 52a. Since the guide rail 55 is not axiallymovable in the pressure beam 23a, it moves up and down with the pressurebeam 23a and is guided together with the sliding rails 57 and 58 guidedthereon in the vertical direction in the vertical guiding devices 54 and56.

The pressure beam 23a may have a rectangular or any other desired crosssection, but it is advantageously box shaped and provided with aU-shaped rail b (FIG. 5) set in from above. The ball bearings of therollers 55a are fixed to said U-shaped rail 55b and the rollers run onthe guide rail 55 extending inside the U-shaped rail 55b.

As shown in FIGS. 5 and 6, a rubber or an air cushion a or the like isinserted between the pressure beam 23a and the steel plate 65 in orderto form an elastically resilient pressure beam 23a.

The to-and-fro movements can also be brought about by other means, forinstance by a mechanical displacement of the axles of a return roller inthe horizontal or vertical direction or by a guide roll.

According to the described embodiment of the invention, the workpieces52a moving along a straight line are transversely pre-ground by the twonarrow grinding belts of the transverse grinding mechanisms 17 and 18rotating in opposite directions and are thereafter ground in thedirection of their travel by a wide grinding belt 34, whereby anoutstanding quality of the upper surface of the workpieces 52a isattained by the to-and-fro motions of the longitudinal grindingmechanism 23 cooperating with the two transverse grinding mechanisms 17and 18.

It lies within the scope of the invention alternatively to use anotherform of construction in which the workpieces 52a are passed throughunderneath a stationary longitudinal grinding mechanism while theirlongitudinal axes are held at a certain angle, i.e. oblique, to theoriginal direction of travel, and after the termination of the grindingoperation the workpieces 52a are fed back through the longitudinalgrinding mechanism in the opposite (mirror image) direction onto theoriginal feed-in way, whereby the effective pressing-on surfaces, suchas for example the previously described steel plate 65, are so shiftedthat they are always above the passing-through workpiece.

According to a further embodiment of the invention, the to-and-fromovements of the longitudinal grinding mechanism can be interruptedfollowing the rythm with which the machine is fed with workpieces.Thereby the to-and-fro movements are always only effective in onedirection on the single workpiece, because they are automaticallyswitched, dependent on the speed they are fed in and on their length, bya contact roller arranged in front of the machine.

Instead of a pressure beam also a contact roller may be provided.

While the method of and machine for grinding largearea workpieces hasbeen shown and described in detail, it is obvious that this invention isnot to be considered as being limited to the exact form disclosed, andthat changes in detail and construction may be made therein within thescope of the invention, without departing from the spirit thereof.

What is claimed is:

1. A machine for grinding plate-like large area workpieces comprising:

(a) means mounting a plurality of grinding assemblies on a framestructure,

(b) conveyor means to transport said workpieces sequentially below saidgrinding assemblies,

(0) at least one of said grinding assemblies provides transversegrinding of said workpiece,

(d) at least one of said grinding assemblies provides longitudinalgrinding of said workpiece, and

(e) means to effect periodic back and forth movement of saidlongitudinal grinding assembly transversely to the direction of movementof said workpieces.

2. A machine as claimed in claim 1 wherein said transverse grindingassembly is laterally disposed from said longitudinal grinding assemblyto first receive said workpieces transported by said conveyor means.

3. A machine as claimed in claim 2 wherein said conveyor means includesan endless belt conveyor which carries said workpieces below saidgrinding assemblies.

4. A machine as claimed in claim 3 wherein said transverse grindingassembly includes a vertically movable pressure beam located inside anendless grinding belt having a direction of movement transverse to thedirection of movement of said workpieces.

5. A machine as claimed in claim 4 wherein said transverse grindingassembly includes an endless laminated pressure belt disposed betweensaid endless grinding belt and said pressure beam.

6. A machine as claimed in claim 3 wherein said longitudinal grindingassembly includes a pressure beam located on the inside of an endlessgrinding belt having a direction of movement parallel to the directionof movement of said workpieces.

7. A machine as claimed in claim 6 wherein said longitudinal grindingassembly includes means to press said pressure beam against the insidesurface of said longitudinal grinding belt to effect grinding of saidworkpieces.

8. A machine as claimed in claim 7 wherein there are two transversegrinding assemblies laterally disposed from each other and from saidlongitudinal grinding assembly to first receive said workpiecestransported by said conveyor means.

9. A machine as claimed in claim 8 wherein said conveyor means includesan endless belt conveyor which carries said workpieces below saidgrinding assemblies.

10. A machine as claimed in claim 9 wherein said transverse grindingassembly includes a vertically movable pressure beam located inside anendless grinding belt having a direction of movement transverse to thedirection of movement of said workpieces.

11. A machine as claimed in claim 7, wherein said longitudinal grindingassembly includes a device for adjusting the grinding belt to run in themiddle portion of its drive and guide rollers.

12. A machine as claimed in claim 7, wherein the pressure beam with thedrive for the grinding belt is arranged so as to be able to moveto-and-fro in the machine.

13. A machine as claimed in claim 7, wherein the pressure beam and thegrinding belt with its drive are mounted in lateral end platesdisplacable by a spindle.

14. A machine as claimed in claim 13, wherein the lateral end plates aremounted on a guide member arranged in the machine transverse to thedirection of passage of the workpieces.

15. A machine as claimed in claim 14, wherein the guide member ispivotably mounted in the machine.

16. A machine as claimed in claim 14, wherein the guide member isconstructed to have a cross section like a circle, a rectangle and thelike with guideways arranged on opposing sides or edges for guidingrollers carrying the lateral end plates.

17. A machine as claimed in claim 7, wherein the pressure beam has apressing surface which is variable by means of an adjustment mechanism.

18. A machine as claimed in claim 17, wherein a steel plate is providedto serve as the pressing surface of the resilient pressure beam, whichsteel plate is held in a lowered position where the grinding is takingplace in the area of the effective pressing surface and in a raisedposition on the outer edges by lifting rods and pivotable levers.

19. A machine as claimed in claim 18, wherein the free ends of thepivotable levers are guided by means of rollers on two sliding railsextending parallel to the pressure beam and leaving a free space betweenthem which corresponds to the desired elfective pressing surface.

20. A machine as claimed in claim 19, wherein the free space between thesliding rails is adjustable as to length by the adjustable mounting ofthe sliding rails.

21. A machine as claimed in claim 19, wherein the sliding rails aremounted movably on a guide rail extending through the width of themachine.

22. A machine as claimed in claim 21, wherein the pressure beam isguided on the guide rail by means of rollers.

23. A machine as claimed in claim 21, wherein the pressure beam is boxshaped and guided on the guide rail in its inside by rollers.

24. A machine as claimed in claim 7, wherein the pressure beam isconnected by levers with a shaft which can be turned by means of apressure-controlled adjustment apparatus.

References Cited UNITED STATES PATENTS 3,364,626 1/1968 Keyes 51-1382,363,039 11/1944 Baldenhofer 5l3 1,191,045 7/1916 Verner 51.3 634,32510/1899 Chain 51--302 JAMES L. JONES, JR., Primary Examiner US. Cl. X.R.51--137

